Noroviruses are the most common cause of acute gastroenteritis (infection of the stomach and intestines) in the United States. Norovirus illness spreads easily and is often called stomach flu.
People who are infected can spread it directly to other people, or can contaminate food or drinks they prepare for other people. The virus can also survive on surfaces that have been contaminated with the virus or be spread through contact with an infected person.
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How contagious is norovirus?
Just a very small amount – as few as 18 viral particles – of norovirus on your food or your hands can make you sick. In fact, the amount of virus particles that fit on the head of a pin would be enough to infect more than 1,000 people!
Source: Journal of Medical Virology, August, 20
Norovirus Case Study
In May 2017 – nearly 1,000 students, teachers and staff in 32 schools in northern California’s Yolo County have contracted the gastrointestinal illness norovirus. Aside from public schools, the University of California, Davis, was also affected. Yolo County includes the area west of Sacramento.
Some districts were hit harder than others. The Woodland Joint Unified School District was hit hardest with 434 cases, while Davis Joint Unified School District counted 181 infections.
The virus started to spread in early May when 33 students and five teachers were hit with the bug, according to the Sacramento Bee.
Source: Sacramento Bee: http://www.sacbee.com/news/local/education/article150324507.html
Each year on average in the United States, norovirus:
- Causes 19–21 million cases of acute gastroenteritis (inflammation of the stomach or intestines or both);
- Leads to 1.7–1.9 million outpatient visits and 400,000 emergency department visits, primarily in young children;
- Contributes to about 56,000–71,000 hospitalizations and 570-800 deaths, mostly among young children and the elderly.
Where do norovirus outbreaks from food contamination happen?
- Restaurant: 64%
- Catering or Banquet facility: 17%
- Private Residence: 4%
- Health Care Facilities: 1%
- Schools and Daycare: 1%
- Other/multiple: 13%
Source: CDC National Outbreak Reporting System, 2009-2012
CDC Video: have you ever heard of Norovirus
About Norovirus Illness
|Sources||Produce, shellfish, ready-to-eat foods touched by infected food workers (salads, sandwiches, ice, cookies, fruit), or any other foods contaminated with vomit or feces from an infected person|
|Incubation Period||12-48 hours|
|Symptoms||Diarrhea, vomiting, nausea,and stomach pain. Diarrhea tends to be watery and non-bloody. Diarrhea is more common in adults and vomiting is more common in children|
|Duration of Illness||1-3 days. Among young children, old adults, and hospitalized patients, it can last 4-6 days.|
|What Do I Do?||Drink plenty of fluids and get rest. If you cannot drink enough fluids to prevent dehydration, call your doctor.|
|How Do I Prevent It?||
Food Workers with Norovirus Illness Can Spread the Virus to Others
People who have norovirus illness can shed billions of norovirus particles.
You are most contagious:
- when you are sick with norovirus illness, and
- during the first few days after you recover.
If you work with food when you have norovirus illness, you can spread the virus to others. You can easily contaminate food and drinks that you touch with bare hands. People who consume the food or drinks can get norovirus and become sick. This can cause an outbreak.
Outbreaks of norovirus illness occur in nursing homes, hospitals, restaurants, cruise ships, schools, banquet halls, summer camps, and even at family dinners. These are all places where people often eat food handled or prepared by others.
Norovirus is the leading cause of illness and outbreaks from contaminated food in the United States, Most of these outbreaks occur in the food service settings like restaurants. Infected food workers are frequently the source of the outbreaks, often by touching ready-to-eat foods, such as raw fruits and vegetables, with their bare hands before serving them. However, any food served raw or handled after being cooked can get contaminated with norovirus.
Norovirus outbreaks can also occur from foods, such as oysters, fruits, and vegetables, that are contaminated at their source.
Ways that Food Workers Can Help Prevent Norovirus from Spreading
Food workers can follow some simple tips to prevent norovirus from spreading:
- Avoid preparing food for others while you are sick and for at least 48 hours after symptoms stop
- Wash your hands carefully and often with soap and water
- Rinse fruits and vegetables and cook shellfish thoroughly
- Clean and sanitize kitchen utensils, counters, and surfaces routinely
- Wash table linens, napkins, and other laundry thoroughly
Norovirus in Restaurants and Catered Events
Most norovirus outbreaks from contaminated food occur in food service settings like restaurants. Infected food workers are frequently the source of these outbreaks, often by touching ready-to-eat foods, such as raw fruits and vegetables, with their bare hands before serving them. Foodborne outbreaks of norovirus illness have also occurred in banquet halls, and even at family dinners, where people eat food handled or prepared by others.
Norovirus outbreaks can also occur from fecal (stool) contamination of certain foods at their source. For example, oysters harvested from contaminated water and raspberries irrigated with contaminated water have caused norovirus outbreaks.
Norovirus on Cruise Ships
Over 90% of diarrheal disease outbreaks on cruise ships are caused by norovirus. Norovirus can be especially challenging to control on cruises ships because of the close living quarters, shared dining areas, and rapid turnover of passengers. When the ship docks, norovirus can be brought on board in contaminated food or water or by passengers who were infected while ashore. Repeated outbreaks on consecutive cruises may also result from infected crew or environmental contamination. This is because norovirus can persist on surfaces and is resistant to many common disinfectants.